Windows 8.1 Update is now available via Windows Update, although it may take a while before it rolls out to your systems. See what's new and this blog post with more information. There is also a nice best of BUILD post you may find useful as well.
See KB 2919355
Note that this update is mandatory. All future servicing for Windows 8.1, Windows RT 8.1, and Windows Server 2012 R2 will be based on having this update installed. Windows 8.1 Update includes a roll-up of servicing changes to date.
MSDN/TechNet Subscribers: This is available as both a standalone update and as a full Windows 8.1 ISO with the update included.
Windows XP: In other news, as of today Windows XP is now end-of-life. See this blog post for my homage to this venerable OS...
Image may be NSFW.Clik here to view.
